This is a Phase II study designed to estimate the efficacy of weekly low-dose PEG-Intron in pediatric patients with CNS tumors, beginning 2-10 weeks after completion of radiation therapy. The endpoint of the trial is 2-year survival compared to historical controls who have received radiation alone. Patients will also undergo extensive imaging analysis. To date, 30 patients have been enrolled. All patients have tolerated the PEG-Intron therapy well, with no adverse events directly attributable to the study agent. The study is ongoing.